If you DO want the names to go together in some way, it doesn't have to be the way the names look or sound or what culture they come from. You could look for names with similar meanings. Or, since the name Sansa comes from a character in a book, maybe your other names could be literary references as well.

Also, even though Sunniva has many of the same letters as Sansa, they don't sound the same or matchy to me. I think Sunniva is really nice. I had never heard of it before.

AgnesEulalie is my favorite. It sounds so great next to Sansa Nanami, and makes so much sense. Adelaide just doesn't make sense at all next to Sansa. I see it as stuffy to go-with-the-flow. Agnes has been seen as a hard name for a long time, but I see it as chic and booky, but when paired with Eulalie, its really creative and care-free, just like Sansa Nanami.

southern.maple: I like how you put it about the middle names' feel balancing the first names. That's a good idea, something I hadn't given much thought to.

shvibziks: Michiko is a beautiful name. I find most Japanese girl names lovely, which while giving me many to choose from, makes it hard to narrow down my favorites, haha!

thatkathryngirl: I don't think I need them to go together 100% but I'll admit I do like when there's something bridging sibling's names (when it's somewhat subtle). For example, on the boys' side of things, one sibling set I liked was to have two boys named Léo Shinobu & AlfredMarch. The middle names went together to me because Shinobu means "enduring" and March reminds me of marching on, or keeping on with life... so the meanings are complementary in a way.

Sansa, meaning wise, I'm not clear on. I heard it first in the novels, but I can't seem to track down a definite name meaning. The only thing I have run across is it being related to the name Sancha, meaning pious/holy. Which as meanings go, doesn't really do much for either of us (not atheist, but not religious either). But, perhaps, a name with a light meaning, like Lucia? For some reason religion-related things remind me of "light."

Sunniva I just came across on this site, so I don't know a lot about it yet. I've been pronouncing it soo-nee-vuh, but I'm not even sure that's correct.

liviajoan: Thanks! I am partial to Eulalie. It sounds so quirky and cute to me, and the name meaning, "Well-spoken" is wonderful. That's something that's important to me.

moving to new account with username I like more... since we can't just change them